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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Fiberoptics for liquid propellant rocket engine environments

Interest is increasing in the use of fiberoptics on liquid-fueled rocket engines in recognition of their immunity to lightning and EMI, light weight, high-frequency response, and the possibility offered by optical technologies to measure additional important engine parameters for which present measurement methods are impractical. This paper discusses the requirements to be placed on fiberoptics applied to liquid-fueled rocket engines; identifies manufacturers of fibers that appear to have promise for the harsh rocket engine applications; and summarizes information on the characteristics of these fibers obtained from the manufacturers, program testing, and the general literature.

Delcher, R.↗
NASA NTRS1989

Thermal coefficient of delay for various coaxial and fiber-optic cables

Data are presented on the thermal coefficient of delay for various coaxial and fiber optic cables, as measured by the Frequency and Timing Systems Engineering Group and the Time and Frequency Systems Research Group. The measured pressure coefficient of delay is also given for the air-dielectric coaxial cables. A description of the measurement method and a description of each of the cables and its use at JPL and in the DSN are included. An improvement in frequency and phase stability by a factor of ten is possible with the use of fiber optics.

Lutes, G. F.↗
NASA NTRS1990

Proposed aerothermodynamic experiments in transition flow using the NASA/ASI tethered satellite system-2

Aerothermodynamic, aerodynamic, and atmospheric science data acquired between 55 and 150 km has been limited by the lack of vehicles or platforms capable of sustained operation at these altitudes. Tethered satellites, which have been under study for this purpose by NASA, the Italian Space Agency (ASI), and others for more than a decade, are expected to become a reality by mid-1991. This approach, in which an instrumented platform is maintained at a desired altitude by a tether attached to a host vehicle orbiting at higher altitudes, will provide the first opportunity to obtain steady state data over an extended period encompassing one or more orbital revolutions. This paper describes the objectives and measurement methods for the first of the facility-class satellites, the TSS-2, which is proposed for a 1995 deployment, and gives the status of the experiment definition. Monte Carlo modeling of the flow fields at 130 km around the baseline 1.6 m diameter sphere is discussed and illustrative results of the modeling given.

Wood, George M.↗
NASA NTRS1990

Relationship of radar cross section to the geometric size of orbital debris

An accurate determination of the sizes of orbiting debris objects is essential to predicting collision rates, atmospheric decay rates, and fragmentation laws for orbiting objects. The radar cross section (RCS) is the most common means of estimating the size of orbiting objects. However, the RCS is prone to error due to Mie scattering, compositional effects, geometrical effects, tumbling, and other dependencies. Optical measurement methods are theoretically much more accurate, but necessitate estimates of the object's albedo. This paper examines the relationship of RCS and optical cross section to physical size and albedo, and presents rules useful for quantizing the physical size of space objects.

Badhwar, Gautam D.↗
NASA NTRS1991

Development Of Composite Panels For Telescope Mirrors

Report describes continuing program for development of lightweight hexagonal graphite/epoxy composite panels intended to support precisely curved mirror surfaces assembled into large telescope mirror. Discusses development requirements, technical decisions, fabrication methods, measurements of properties of materials, analytical simulation, and thermal vacuum testing. Telescope flown in orbit around Earth to observe at wavelengths down to 30 micrometers.

Freeland, Robert E.↗
NASA NTRS1990

Earth Observing Scanning Polarimeter (EOSP), phase B

Evaluations performed during a Phase B study directed towards defining an optimal design for the Earth Observing Scanning Polarimeter (EOSP) instrument is summarized. An overview of the experiment approach is included which provides a summary of the scientific objectives, the background of the measurement approach, and the measurement method. In the instrumentation section, details of the design are discussed starting with the key instrument features required to accomplish the scientific objectives and a system characterization in terms of the Stokes vector/Mueller matrix formalism. This is followed by a detailing of the instrument design concept, the design of the individual elements of the system, the predicted performance, and a summary of appropriate instrument testing and calibration. The selected design makes use of key features of predecessor polarimeters and is fully compatible with the Earth Observing System spacecraft requirements.

Source record↗
NASA NTRS1991

High power arcjet

The activities of the High Power Arcjet Project (HIPARC) from August 1990 to January 1991 are discussed. In this period the HIPARC thruster was ignited for the first time. Power levels up to 140 kW with a mass flow rate of 300 mg/s hydrogen were reached. Specific impulse values of more than 1300 s were shown to be possible. Tests were performed with the baseline thruster version only, which has a 6 mm throat diameter and a conical nozzle with a 20 degree half angle. Measurement data summing up all tests carried out until now is included. All measuring methods are described, including a check on possible error sources.

Goelz, T. M.↗
NASA NTRS1991

Urodynamic pressure sensor

A transducer system was developed for measuring the closing pressure profile along the female urethra, which provides up to five sensors within the functional length of the urethra. This new development is an improvement over an earlier measurement method that has a smaller sensor area and was unable to respond to transient events. Three sensors were constructed; one of them was subjected to approximately eight hours of use in a clinical setting during which 576 data points were obtained. The complete instrument system, including the signal conditioning electronics, data acquisition unit, and the computer with its display and printer is described and illustrated.

Moore, Thomas↗
NASA NTRS1991

The NASA Ocean Data System at the Jet Propulsion Laboratory

Global change studies require satellite oceanographic observations archived in an active data center. This paper describes the activities of an experimental active oceanographic data archive center specializing in distribution of high-level oceanographic data products produced by research oceanographers from satellite altimeter, scatterometer, and microwave and infrared radiometer measurements. Methods to encourage data sharing practices were developed. Services initiated to help oceanographers conduct research more effectively included rapid delivery of data, reprocessing data sets, subsetting of large data sets, and distribution of multiple data sets on a single medium.

Halpern, David↗
NASA NTRS1990

Measurement of structure motion by means of a moving light sheet

The elaboration of an optical system which measures the displacement and velocity of large flexible space structures is reviewed. The motion-measuring system, comprised of a laser, optics, motorized mirror, two photodiodes and electronics, is designed to allow feedback for configuration control of flexible structures. A motor or scanner is employed to sweep the light sheet. The range of motion was shown to be 2 inches, and information was received at a rate of 30 Hz. The uncertainty in displacement measurement was better than +0.01 inch from a distance of 16 feet. The results are considered to be very good for two scanning light sheet systems. Higher sample rates and a more constant speed would improve the rotating mirror option, and the accuracy and range of the scanning mirror option could be upgraded as well. Both setups are shown to be viable noncontact measuring methods for the displacement and velocity of large space structures.

Tcheng, Ping↗
NASA NTRS1991

Laser interferometer/Preston tube skin-friction comparison in shock/boundary-layer interaction

An evaluation is conducted of the accuracy of the 'Preston tube' surface pitot-pressure skin friction measurement method relative to the already proven laser interferometer skin-friction meter in a swept shock wave/turbulent boundary-layer interaction. The Preston tube was used to estimate the total shear-stress distribution in a fin-generated swept shock-wave/turbulent boundary-layer interaction. The Keener-Hopkins calibration method using the isentropic relation to calculate the Preston-tube Mach number produces the best results.

Kim, K.-S.↗
NASA NTRS1991

Work performed on velocity profiles in a hot jet by simplified RELIEF

The Raman Excitation + Laser Induced Electronic Fluorescence (RELIEF) velocity measurement method is based on vibrationally tagging oxygen molecules and observing their displacement after a short period of time. Two papers that discuss the use and implementation of the RELIEF technique are presented in this final report. Additionally, the end of the report contains a listing of the personnel involved and the reference documents used in the production of this final report.

Miles, Richard B.↗
NASA NTRS1992

A dynamic study of fragmentation and energy loss during high velocity impact

Research conducted under this contract can be divided into two main areas: hypervelocity (in the range up to 7 km/s) and high velocity (less than 1 km/s). Work in the former was performed at NASA-MSFC using the Light Gas Gun Facility. The lower velocity studies were conducted at Auburn University using the ballistic gun. The emphasis of the project was on the hypervelocity phenomenon especially in the characterization of the debris cloud formed by the primary impact events. Special devices were made to determine the angular distributions of momentum and energy of the debris cloud as a function of impact conditions. After several iteration processes, it was decided to concentrate on the momentum effort. Prototype devices were designed, fabricated, and tested. These devices were based on the conservation of momentum. Distributions of the debris cloud formed were measured by determining the amount of momentum transferred from the debris cloud to strategically placed pendulum measurement devices. The motion of the pendula was monitored using itegrated opto-interrupters. The distribution of momentum in the debris cloud was found to be a strong function of the impact condition. Small projectiles at high velocities were observed to produce finely dispersed debris whereas large projectiles generated discrete particles in the debris. Results also show that the momentum in the forward direction was enhanced due to the impact. This phenomenon of momentum multiplication was also observed in other studies and in computer simulations. It was initially planned to determine the energy distribution using deformation energy in a rod with strain gauges. Results from preliminary studies show that this technique is acceptable but too tedious. A new technique was explored based on measuring the heating effect of the debris cloud using an IR camera. The feasibility and sensitivity was established at Auburn University. This type of energy distribution measurement method can easily be adapted to the gas gun facility at MSFC. The objective of the lower velocity studies at Auburn was to simulate the damage produced in advanced materials by the lower energy debris cloud.

Zee, Ralph H.↗
NASA NTRS1993

Spectroscopic investigation of a low-power arcjet plume

We report the results of spectroscopic measurements on the exhaust plume from a 1 kW NASA Lewis arcjet operated on simulated ammonia. In particular, we analyze emissions from the Balmer lines of atomic hydrogen and from one of the rotational bands of the NH radical. We find that exit plane temperatures are in the range 2000 to 3500 K, depending on the measurement method, and that the electron density upstream of the exit plane is on the order of 1.5 x 10 exp 14/cu cm as determined by the Stark width of the Balmer-alpha line. Also, we have determined that the average velocity of atomic hydrogen at the exit plane is about 4 km/sec, and that strong acceleration (to 5.5 km/sec) of the flow occurs just beyond the exit plane.

Ruyten, W. M.↗
NASA NTRS1939

Experiments on a Slotted Wing

The results of pressure distribution measurements that were made on a model wing section of a Fieseler F 5 R type airplane are presented. Comparison of those model tests with the corresponding flight tests indicates the limitations and also the advantages of wind tunnel investigations, the advantages being particularly that through the variety of measuring methods employed the more complicated flow conditions may also be clarified. A fact brought out in these tests is that even in the case of "well rounded" slots it is possible for a vortex to be set up at the slot entrance and this vortex is responsible for certain irregularities in the pressure distribution and in the efficiency of the slot.

Ruden, P↗
NASA NTRS1994

Strain gage selection in loads equations using a genetic algorithm

Traditionally, structural loads are measured using strain gages. A loads calibration test must be done before loads can be accurately measured. In one measurement method, a series of point loads is applied to the structure, and loads equations are derived via the least squares curve fitting algorithm using the strain gage responses to the applied point loads. However, many research structures are highly instrumented with strain gages, and the number and selection of gages used in a loads equation can be problematic. This paper presents an improved technique using a genetic algorithm to choose the strain gages used in the loads equations. Also presented are a comparison of the genetic algorithm performance with the current T-value technique and a variant known as the Best Step-down technique. Examples are shown using aerospace vehicle wings of high and low aspect ratio. In addition, a significant limitation in the current methods is revealed. The genetic algorithm arrived at a comparable or superior set of gages with significantly less human effort, and could be applied in instances when the current methods could not.

Source record↗
NASA NTRS1994

Using a temperature-controlled quartz crystal microbalance in a space equipment cleanroom to monitor molecular contamination

There is a need for continuous monitoring for molecular contamination in clean rooms where spaceflight equipment is assembled, integrated, and tested to insure that contamination budgets are met. The TQCM (temperature-controlled quartz crystal microbalance) can be used to provide both a real time warning and a cumulative measurement of molecular contamination. It has advantages over the other measurement methods such as witness mirrors, NVR (non-volatile residue) plates, and gas analyzers. A comparison of the TQCM sensitivity and ease of operations is made with the other methods. The surface acoustic wave microbalance (SAW), a newly developed instrument similar to TQCM, is considered in the comparison. An example is provided of TQCM use at Goddard Space Flight Center when the Wide Field Planetary Camera 2(WFPC-2) and the Corrective Optics Space Telescope Axial Replacement (COSTAR) were undergoing integrated testing prior to their installation in the Hubble Space Telescope on its first servicing mission. Areas for further investigation are presented.

Mitchell, William J.↗
NASA NTRS1995

Two color holographic interferometry for microgravity application

Holographic interferometry is a primary candidate for determining temperature and concentration in crystal growth experiments designed for space. The method measures refractive index changes within the fluid of an experimental test cell resulting from temperature and/or concentration changes. When the refractive index changes are caused by simultaneous temperature and concentration changes, the contributions of the two effects cannot be separated by single wavelength interferometry. By using two wavelengths, however, two independent interferograms can provide the additional independent equation required to determine the two unknowns. There is no other technique available that provides this type of information. The primary objectives of this effort were to experimentally verify the mathematical theory of two color holographic interferometry (TCHI) and to determine the practical value of this technique for space application. In the foregoing study, the theory of TCHI has been tested experimentally over a range of interest for materials processing in space where measurements of temperature and concentration in a solution are required. New techniques were developed and applied to stretch the limits beyond what could be done with existing procedures. The study resulted in the production of one of the most advanced, enhanced sensitivity holographic interferometers in existence. The interferometric measurements made at MSFC represent what is believed to be the most accurate holographic interferometric measurements made in a fluid to date. The tests have provided an understanding of the limitations of the technique in practical use.

Trolinger, James D.↗